When you CHOOSE to put 4 couples and a child into 3 bedrooms, I'm not really sure where the complaint is... The features that are being criticized are spelled out very clearly in the listing description. The listing is described in detail both in pictures and words as having small bedrooms, a basic kitchen, and no common area except the large waterfront lanai. There is bed space for up to 11 people if you choose to use all of it -- which would mean up to 4 people per room. Generally this would include families with children in the same room rather than adult couples doubling up in a bedroom. But your budget and preferences should drive the decision. Failure to either read or explain to your friends what to expect is not a basis for complaint.
If anything, this booking demonstrates that a group with zero local familiarity and nominal boating experience can successfully mount a scalloping trip with direct access and unmatched proximity to the water. If being on the water and surrounded by nature are what you want, then this is a good option. But it is definitely small for a Multi-Family vacation.